A numerical study on the dynamic behavior of concrete bridges by pounding effect

When a large earthquake occurs, there is a possibility of pounding between a bridge girder and an abutment. Therefore, existing specifications for highway bridges in JAPAN recommend that necessary gap between the ends of two adjacent girders shall be taken for preventing a collision between a superstructure and an abutment. But if expansion gap is large, a superstructure is able to slide in the horizontal under ground motion and so a bridge pier takes a large burden by seismic load. Recently, some researchers have proposed a new design concept that expansion gap size becomes small and pounding between girder and abutment is permitted. Main objectives of this concept are to control displacement of bridge superstructure with considering the horizontal resistance of abutment by pounding. However this concept has not yet led to be introduced into the seismic design of bridge. The reason is that damage conditions of a superstructure and an abutment by pounding have not ever quantitatively estimated. So in this study, to evaluate the damage condition of an abutment by pounding, impact response analyses of pounding effect were conducted by using 3-dimensional FEM. Furthermore, to clarify dynamic behavior of whole bridge under pounding, frame analyses were conducted.